Film intermittent advancing mechanism



JuEy 12, 1955 2,712,771

W. R. ISOM FILM INTERMITTENT ADVANCING MECHANISM Filed April 30, 1952 2Sheets-Sheet l llllllllllllllilu lllll INVENTOR Harman R. I5 [1111 BYATTORNEY July 12, 1955 w. R. ISOM FILM INTERMITTENT ADVANCING MECHANISM2 Sheets-Sheet 2 Filed April 30, L952 FEST C/CLE) INVENTOR [[[arrenRlsmn BY ATTOiQNEY I I I United States Fatent r: a he Ag Patented. ulyEL, ".5955

2,712,771 FILM IN TERMITTEN T AD VANCING MECHANISM Application April 30,1952, Serial No. 285,20?

11 Claims. (Cl. 88-18.4)

termittent using a pin wheelstar wheel combination and the cam-claw tye. With the advent of kinescope photography, whereby the cameraphotographs televi sion pictures on kinescope era is desirable. theprojector should have a special film advancing mechanism.

simultaneous pick-up devices are totally successful. Furthermore,dependence upon storage type pick-up tubes with their attendant shadingdilliculties is no longer necessary for deriving video signals frommotion picture film.

The present invention, therefore, is directed to a serially arrangedcombination of the Geneva and claw types of pull-down film mechanismswhich provide the desired film advancing cycle for television purposes.The

is avoided, which permits a better utilization of a light source.

The principal object of the invention, therefore, is to facilitate theadvancement of motion picture film in a camera and projector.

Another object of the invention is to provide an improved film advancingmechanism for cameras and projectors.

A further object of the invention is to provide an improved filmpull-down mechanism at twenty-four frames per second, which iscompatible with the vertical blanking time of a thirty-frame televisionsystem.

Although the novel features which are believed to be characteristic ofthis invention will be pointed out with particularity in the appendedclaims, the manner of its Geneva H the sixty per Fig. 6 is a graphshowing the relationship between the vertical blanking pulses and thefilm advancing periods.

Referring now to the drawings, in which the same nuelements, themechanism is driven by a constant speed belt 5 of the rubber toothedtype, over a sprocket 6. The sprocket is on a shaft 7 with a collar 8and extends Within a casing 1E and on which is a pin wheel 11. The Wheel11 has two pins 13 and 14 extending therefrom (see Fig. 4), these pinsbeing spaced 144 and 216 degrees apart. The pins are adapted to wheel16, which has three equally spaced slots therein. The pin wheel 11 andstar wheel 16 comprise the Geneva portion of the mechanism.

Gn the shaft 17 of the star wheel 16 is a herring bone gear 33 in meshwith a herring bone gear 19 on a shaft These gears are preferably ofnylon because of the high ratio between sheer strength of the teeth andmass of the gears and because they are light in weight with a lowrotational inertia. They are somewhat resilient and ease the shock loadon the Geneva. The ratio of gear 122 to gear 19 is three to one. Also,on shaft 25 is a flat cam 22 attached to collar 23 and a triangularconstant diameter cam 25, this triangular cam being within a shuttle.26. The cam 25 provides the film pull-clown cycle and may be consideredas the up-and-down cam, and the cam 22, the in-and-out motion of thefilm pulldown claw.

fixedly attached to shuttle 26 is a hollow rod 23 which is slidaoie androtatable in a bearing plate At the upper end of the rod there isattached a claw member 31 having right angle tee h 32 and 33, which areadapted to enter and be withdra'tvn from the perforations 34 of a film35 as the rod is alternately rotated. The shuttle rod is hollow toreduce inertia, and serves as the pivot around which the in-andou'rmotion of the claw takes place. The rod is attached to the shuttle insuch a location that the force of the pull-down from the cam 25 isexerted d'"ectly in line v he rod, which prevents moment arms and avoidsbinding. This reduces wear and flexing of the parts and preventsbreakage. Stops, not shown, are p vided to prevent the claw fromovershooting when it is withdrawn from the film.

Rotation of cam 25 provides the film, while cam 22 moves the teeth 32and 33 in and out of the film. The latter action is accomplished by thecam follower 37 on rod 38 attached to linkage 39 on shuttle 26. Thismechanism is spring loaded by spring 41. By limiting the shuttlemovement, a light spring may be used which prevents excessive loading ofthe intermittent. All the moving elements from pin wheel to earn operatein a live spray of lubricant.

Referring now to Fig. 6, the non-compatibility between second verticalblanking pulses and the standard motion picture periods of arty-fourframes per second. and the compatibility hetwe .e sixty per secondvertical blanking pulses and the 2-3 intermittent at twenty-four framesper second are shown. it is noted that the pull-down shown by the shortheavy iines for the 2-3 intermittent occurs only during the blankingtimes, while some of the pull-downs for the standard intermittent occurduring the scanning Since the pins 13 and Ltd are spaced as shown in 4,the 2-3 interz'nittcnt periods are obtained. The belt sprocket 6 isdriven at /"'1 R. P. M. or 12 l. 5., which is the speed of the pin wheelll. Since only two pins are used per revolution of the pin wheel and thestar wheel 16 has three grooves therein, the star wheel intermittentlyrotates at an average speed of 8 R. P. S. Of course, the gear it? ha theform of speed. Since the ratio between gear.

advancement of the is three to one, gear 19 intermittently rotates at anaverage speed of 24 R. P. S., which is also the rotational speed ofearns 22 and 25. Thus, the claw teeth 32 and 33 advance the filmintermittently at 24 frames per second in a 23 order, as shown in thecentral portion of Fig. 6.

To illustrate a complete pull-down cycle or the displacement of claw32-33 for one revolution of cams 22 and 25, reference is made to Fig. 5,wherein the rest periods are shown at a and b, the two up periods at cand d, the in-and-out periods of the claw teeth at e and f,respectively, and the pull-down period at g. The point h is the highestpoint of peak velocity and speed. The peak rotational speed amassed by te cam 25 at this point is approximately 13,956 R. P. M., while thelinear velocity of the claw is approximately 359 inches per second.

By reference to Fig. 4, the time of the pull-down can be calculated. Thepin wheel circle is shown with its center at A, and the star wheelcircle has its center at C. The pins P and P1 are shown with theircenters on the pin wheel circle. The lines BC, DC, and EC represent thethree grooves or slots of the star wheel, each groove being 120 degreesfrom the others, making the right triangles ABC and ACD. Thus, if AB is1, AC is 2 divided by the square root of 3, or 1.1547.

The smallest possible rotation of the pin wheel to produce forty degreesrotation of the star wheel after pin P has entered slot CB, will beequally divided about centerline AC, or, it occurs while slot EC ispassing from B1 to B2. Angle B1CA is twenty degrees and its oppositeside is 1, and although angle ABIC is not known, its opposite side is1.1547. Now, by the laws of sines, it is found that the angle ofrotation of the pin wheel to produce twenty degrees rotation of the starwheel is three degrees, fifteen minutes. This is one-half the pull-downangle, the full angle being six degrees, thirty minutes. However, sincethe film is allowed to overshoot .003 inch, the claw moves this distancebefore it contacts the film. Using these figures, it is found that eightpercent vertical blanking time of a television system is eleven degrees,thirty-two minutes of the twenty-four cycles per second film system.

To improve film life and film steadiness in a rapid film pull-downmechanism as described above, the teeth 32 and 33 of the claw areconstructed as disclosed and claimed in my copending application, SerialNo. 290,442, filed May 28, 1952.

I claim:

1. An intermittent film pull-down mechanism for advancing a motionpicture film at the rate of substantially 1.336 milliseconds per framecomprising a pin wheelstar wheel mechanism, means for driving said pinwheel at a substantially constant speed, a pair of cams, a common shaftfor said cams, gear means interconnecting said stair wheel and saidshaft, and a shuttle and claw mechanism connected to said cams andactuated thereby, said shuttle and claw mechanism being given arectilinear motion by one of said cams and a rotary motion by the otherof said cams perpendicular to said first-mentioned motion.

2. An intermittent film pull-down mechanism in accordance with claim 1,which said pin wheel continuously rotates at twelve R. P. 5., said starwheel intermittently rotates at an average speed of eight R. P. S., andsaid cm shaft intermittently rotates at an average speed of twenty-fourR. P. S.

3. An intermittent film pull-down mechanism in accordance with claim 1,in which said pin wheel continuously rotates at twelve R. P. 8., saidstar wheel being rotated intermittently two-thirds of a revolution perrevolution of 4 said pin wheel, said pin Wheel having two pins spaced144 and 216 degrees apart.

4. An intermittent film pull-down mechanism in accordance with claim 1,in which said shuttle and claw mechanism includes a shuttle actuated byone of said cams for advancing film, and a spring loaded pin actuated bysaid other cam for advancing and retracting said claw to and from saidfilm.

5 An intermittent film advancing system for advancing at a high pulldownspeed twenty-four frames of film per second in a 2 3 ratio, comprising acontinuously driven pin wheel, pins on said wheel spaced-l44 and 216degrees apart, a triple slotted star wheel actuated by said pins, ashaft driven by said star wheel at triple the speed of said star wheel,cams on said shaft, a shuttle bodily translated in a rectilineardirection by one of said cams and vibrated in a rotary direction atsubstantially right angles to said first direction of translation ofsaid shuttle by another of said cams; and a film claw connected to saidshuttle.

6. An intermittent film advancing system in accordance with claim 5, inwhich said pin wheel rotates at twelve R. P. 8., said star wheel at anaverage speed of eight R. P. S., and said cam shaft at an average speedof twentyfour R. P. S.

7. An intermittent film advancing system in accordance with claim 5, inwhich said first mentioned cam translates said shuttle in one directionin substantially the same time period as that of the vertical blankingtime period of a thirty frame television system.

8. An intermittent film advancing system in accordance with claim 5, inwhich said first mentioned cam translates said shuttle in one directionin substantailly 1.336 milliseconds.

9. An intermittent film advancing system for advancing film at a highpulldown speed comprising a continuously driven pin wheel, a pair ofpins on said wheel, a star wheel having slots therein, said star wheelbeing intermittently driven when one of said pins passes in and out ofone of said grooves, a shaft for said star wheel, a second shaft,intermeshing gears on said shafts, a pair of cams on said second shaft,a shuttle on one of said cams, said cam translating the position of saidshuttle rectilinearly, and connecting means between said shuttle andsaid other cam for vibrating said shuttle in a rotary motionsubstantially perpendicular to said motion of translation of saidshuttle.

10. An intermittent film advancing system in accordance with claim 9, inwhich a film moving claw is provided on said shuttle and said connectingmeans includes a spring loaded pin actuated by said other cam.

11. An intermittent film advancing system in accordance with claim 10,in which a rod interconnects said claw and shuttle, said rod being movedaxially by said shuttle for moving said claw to advance said film, saidrod forming a pivot about which said claw is rotatable for moving saidclaw in and out of said film by said spring loaded pin connected to saidshuttle.

References Cited in the file of this patent UNlTED STATES PATENTS

